1. Field of the Invention
The invention relates to a distant measurement method, and more particularly to a distant measurement method utilizing phase shift variation of light beams to estimate distance and a distant measurement system applied therewith.
2. Description of the Related Art
With the development of electronic techniques and semiconductor laser elements, palm-sized distant measurement devices have been extensively used in the architecture, traffic, graphical reconnaissance and interior decoration fields.
In general, a conventional distant measurement device comprises an emitting module with a built-in light emitting element to emit a light beam and a receiving module with a light receiving element to receive the light beam reflected from a target.
Specifically, the light emitting element and the light receiving element used in a conventional phase-type distant measurement device are made of semiconductor material. Based on the characteristics of the semiconductor material to excitedly emit a light beam to the target by the light emitting element, the light receiving element receives and converts the light beam reflected or scattered from the target and converts to an electrical signal. A phase shifting is obtained by comparing the emitted light beam and the reflected light beam, thus, a distance between the distant measurement system and the target can be estimated.
However, due to the light emitting element respectively emitting a measurement beam and a reference light beam during the measurement process of the conventional phase-type distant measurement device, temperature of the light emitting element is increased as the number of times of the measuring process is increased, thus, changeable noise occurs. Further, if the distance between the target and the distant measurement device is fairly short, the time interval between the measurement light beam and the reference light beam received by the light receiving element may be short, thus negatively influencing precision of distant measurement by forming a mutual interference between the measurement light beam and the reference light beam and causing an unpredictable error in the electrical signal output from the light receiving element.